'Sister Wives' star Kody Brown: I am not a womanizer

"Sister Wives" star Kody Brown has four wives and 17 kids. That's known. But what isn't quite so common knowledge is why he and his family have chosen this polygamist lifestyle.

In a tell-all interview with NBC News' Natalie Morales, the family behind TLC's reality show -- Kody and wives Meri, Janelle, Christine and Robyn -- answer Natalie's questions about polygamy, the revelations in their new book, "Becoming Sister Wives," and more.

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One of the things the family brings up in the tome is Kody's past -- specifically, how he had a lot of girlfriends in high school. Some might say that's not particularly surprising, considering he now has four wives. (He's legally married to only his first wife, Meri.)

In a clip of the interview from TLC, Kody explained the girlfriend tidbit to his host, saying that when he was 14, he was trying to figure out his life as a wild boy and answering his calling to be a spiritual person.

Natalie's response? "So it wasn't that you chose religion to be a womanizer?"

After a stunned silence, Kody replied, "Is that what you think I am, a womanizer?" He went on to defend himself and his family, insisting that he had "done the emotional work" in his relationships with his wives, and "shouldered their needs as much as I could." And also, "I was never womanizing. ... This is NOT an open marriage," he insisted.

Check it out:

The Brown family's five oldest children also sat down with Natalie to talk about their lives. The interview special airs at 10 p.m. on TLC Sunday.